feat: Update documentation surrounding CI and API keys

[easymac]

Status

READY

Description

• Add a new dedicated API Keys page documenting the full lifecycle of API keys: creation, usage, expiration options, permission levels, revocation, migration from login:ci, and security details.
• Rewrite the shared CI authentication snippet to direct users to the console-based API key flow instead of the deprecated shorebird login:ci command. Includes a migration callout noting login:ci tokens remain valid until March 2027.
• Update the FAQ entry for CI usage to point users to the console for API key creation rather than the old CLI flow.

[eseidel]

Amazing!